Answer:
You cannot keep me until you have given me. What am I?
What has 4 fingers and a thumb but isn't alive?
Take it and you will lose or gain more than the others.
I am easy to waste and unstoppable. What am I?
I start in little but I end in full you'll find me in half and complete.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.